The cars departed July 15 from the Chicago Museum of Science and Industry. They are expected to reach their final destination of Claremont, California, about July 25.

Solar car races, held to demonstrate the potential of the cars of the future, have been held for about ten years. This year's race is the longest one so far. About 35 teams are competing.

Each car in the race must be able to operate without power from any external sources, including gas and batteries. Most of the surface area is covered with solar cells, which soak up the sun's rays and power the car at speeds of up to 60 miles an hour.

The cars were designed by engineering students across the United States, who worked diligently to build what they hope will be the fastest car to the finish line.

At the University of Michigan, more than 300 students were involved in building one of the entries. Students at the University of Virginia got support from aerospace giant Boeing.

"The body for our vehicles was sponsored by Boeing," said University of Virginia student and car engineer Brian Nicosia. "They built the body itself, we designed it. We gave them files electronically and they were able to actually build it in their facilities."

The cars in the race must be designed for more than speed. Each car must pass a rigorous inspection and complete a qualifying race before being allowed to compete in the main event.

Asteruro Kagawa, a University of Virginia student, helped operate computerized crash simulations to make sure the university's car was up to par. "They are so strict about the safety issue because we'll be driving on regular highways with normal cars going right by us," he said. "Because of it, the race is providing us with lots of regulation."

The cars in the race weigh about 200 to 400 kilograms (441 to 882 pounds) each and are five to six meters (16.4 to 19.7 feet) long. They are aerodynamically designed for maximum efficiency. Because of this, there isn't even enough room for the driver to be seated behind the wheel. Instead, the drivers are forced to drive while lying down, with their heads raised so they can see the road.

Race officials emphasize that the cars in the event are not a prototype for cars that could be mass-produced in the future. The goal is to see how far such cars can be built to travel.